Method for making artificial rocks, in particular large-scale rock imitations

ABSTRACT

In order to manufacture low-weight, large-scale, artificial rocks resistant to weathering and faithfully rendered as in nature, first a malleable plastic reproduction is made of a natural-rock object. If called for, the reproduction is braced in a second method step, preferably by coating its back side with glass-fiber reinforced plastic. The work mold so manufactured receives a parting compound in a third operational step and thereupon preferably fiberglass mats are inserted and a coat of synthetic resin is applied to make a positive in the shape of a hollow artificial-rock blank. This artificial-rock blank is coated in a fourth operational step with a synthetic resin and fine-grain, preferably multicolored natural sand is deposited on or incorporated into the still moist coat of synthetic resin. Once this coat of synthetic resin with its incorporated natural sand has hardened, the artificial rock has been completed.

FIELD OF THE INVENTION

1. Background of the Invention

The invention concerns a method for making artificial rocks, inparticular large-scale rock imitations.

2. Background of the Invention

It is known how to manufacture artificial rocks from correspondinglydyed concrete. However, such rocks are not weather-proof long-term, thatis, when exposed to water, the concrete dyes are "washed out". Also suchconcrete rocks are comparatively heavy, adversely affecting theirshipping and setup. Lastly, such concrete rocks frequently arerecognized as being imitations even from afar on account of the lack oftypical rock structure and coloring of natural rocks.

SUMMARY OF THE INVENTION

The object of the invention is to create a method with which tomanufacture artificial rocks, in particular large-scale rock imitationsand which avoids the above draw-backs. In particular the rocks made bythe method of the invention shall practically match the color andstructure of natural rocks and furthermore they shall be bothlightweight and weathering-proof over long periods.

This problem is solved by a method which in the invention ischaracterized by the following method steps:

(a) Making a plastic reproduction (negative) of a natural-rock object,for instance a rock,

(b) Removing the reproduction from the natural-rock object and bracingthe reproduction by coating its back side with a hardening plastic, forinstance glass-fiber reinforced plastic,

(c) Following hardening the coating on the back side, rotating thereproduction into an operational position wherein the reproduction canbe used as a work mold,

(d) Introducing a parting compound and a hardening plastic and wherecalled for inserting reinforcing means, for instance fiberglass mats,into the work mold which then are coated with a synthetic resin to shapea positive in the form of a hollow blank of an artificial rock,

(e) Removing the hardened artificial-rock blank from the work mold anddepositing a synthetic resin coat on the blank of artificial rock, and

(f) Depositing and incorporating (embedding) natural sand of finegranularity onto or where called for into the still moist coat ofsynthetic resin and also thereupon drying and hardening the syntheticresin coat with incorporated natural sand.

The method of the invention allows manufacturing in particularlarge-scale, weathering-proof artificial rocks faithful to nature and ofcomparatively low weights. The plastic used to make the reproduction(negative) may consist of economical silicone rubber. Because thisreproduction as yet lacks dimensional stability required of a work mold,it is braced in accordance with feature (b) on the back side by ahardening, preferably glass-fiber reinforced plastic. The blank of theartificial rock preferably is made from a glass-fiber reinforced plasticwhich, however, also may be replaced by a pressure-setting plastic, ahard PVC or by a polyester.

An alternative solution of the above problem is characterized by thefollowing method steps:

(a) Preparing a reproduction (negative) of a malleable and hardeningplastic from a natural-stone object, for instance a rock,

(b) Removing the reproduction from the natural-rock object and rotatingthe reproduction into an operational position in which, followinghardening, the reproduction can be used as a work mold,

(c) Introducing a parting compound and a hardening plastic and wherecalled for inserting reinforcing means such as fiberglass mats into thework mold which then are coated with a synthetic resin to produce apositive in the form of a hollow blank of an artificial rock,

(d) Removing the hardened blank of artificial rock from the work moldand depositing a coat of synthetic resin onto the blank of artificialrock, and

(e) Depositing and incorporating (embedding) a fine-grain, natural sandonto or into the still moist coat of synthetic resin and then drying andhardening the synthetic resin coat with incorporated natural sand.

In this procedure, a malleable plastic is used for making thereproduction, which shall be sufficiently dimensionally stable followinghardening to serve directly as the work mold.

In order to faithfully imitate the color of natural rocks of differentcolorations, multicolored natural sands will be correspondingly andadvantageously deposited on or incorporated into the still moist coat ofsynthetic resin.

Where the artificial stones are imitations for instance of millstones,feeding troughs etc., a monochrome natural sand also can be used. Thepreferred grain sizes of natural sands are in the range from 0.063 to0.63 mm. Depending on the structure of the natural rock, grain sizesfrom 0.63 to 2 mm also may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is elucidated below in relation to the drawing of anillustrative implementation.

FIG. 1 is a side elevational view of a first illustrative step in themethod of manufacturing artificial rocks;

FIG. 2 is a side elevational view of a second step of the method;

FIG. 3 is a side elevational view of a third step of the method; and

FIG. 4 is a side elevational view of a fourth step of the method, alsoshowing a portion thereof enlarged in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the method of the invention, artificial rocks, inparticular large scale rocks can be manufactured as reproductions of themost diverse shapes and colors faithfully reflecting the natural kind.Illustratively they may be used as large-scale rock imitations inlandscaping gardens, in zoological facilities etc. and on a smallerscale as art objects (household fittings). For instance to make animitation rock, a reproduction (negative)2 from a natural rock 1(FIG. 1) is first made using an economical malleable plastic such assilicone rubber. Following its removal from the natural rock 1, thisreproduction 2 must be made dimensionally stable or be braced. For thatpurpose the back side of the reproduction 2 is coated with a glass-fiberreinforced plastic 3 in a second method step (FIG. 2). After hardeningof this backside coat 3, the actual work mold 4 for manufacturing therock imitations is then ready, which merely requires being rotated by180° into an operational position (omitted).

First a parting compound is introduced into the work mold 4 and thenfiberglass mats are inserted and coated with synthetic resin. In thismanner a positive is obtained in the form of a hollow rock blank 5 ofwhich the structure and contour match that of the natural rock 1.

After the hardened rock blank 5 has been removed from the work mold 4(FIG. 3), a coat 6 of synthetic resin is deposited on the blank 5 in afourth method step (FIG. 4) and fine-grained, multicolored natural sandis deposited onto the still moist synthetic resin coat 6 in order tofaithfully imitate the color tones and shades of the natural rock 1.Thereupon the synthetic-resin coat 6 is dried together with theincorporated natural sand and as a result it hardens. The rock imitation7 corresponding to the natural rock 1 is then finished. imitation 7corresponding to the natural rock 1 is then finished.

Preferably the wall thickness of the rock blank 5 shall be about 4 mm,and the synthetic-resin coat 6 with the incorporated natural sandevinces a thickness of about 2 mm. The preferred grain sizes of thenatural sand being used are in the range of 0.063 to 0.63 mm.Advantageously the work mold 4 is reusable several times.

The bracing of the reproduction 2 to create the work mold 4 also can beimplemented using a pressure-setting plastic, a hard PVC or polyesters.

Lastly the reproduction 2 also can be made from a malleable, hardeningplastic of such wall thickness that it shall provide directly upon itshardening the dimensional stability required for its use as work mold.This feature saves one method step.

In lieu of using the glass-fiber reinforced plastic to make the rockblank 5, other materials such as a pressure-setting plastic, a hard PVCor polyesters may be used.

We claim:
 1. A method for manufacturing artificial rocks, in particularlarge-scale rock imitations, comprising the steps of:(a) making amalleable-plastic reproduction negative from a natural stone object, (b)removing the reproduction from the natural-stone object and bracing thereproduction by coating its back side with a hardening plastic, (c)following bracing of the reproduction, moving the reproduction into awork position wherein the reproduction can be used as a work mold, (d)adding a parting compound and a hardening plastic into the work mold andcoating the reproduction with synthetic resin to manufacture a positivein the form of a hardened artificial rock blank, (e) removing thehardened artificial rock blank from the work mold and depositing a coatof synthetic resin onto the artificial rock blank, and (f) depositingand embedding fine-grain natural sand onto and into the still moist coatof synthetic resin and thereupon drying and hardening the coat ofsynthetic resin with its incorporated natural sand.
 2. Method defined inclaim 1, wherein reinforcing means is added into the work mold with thehardening plastic in step (d).
 3. Method defined in claim 2, wherein thereinforcing means is fiberglass mats.
 4. Method defined in claim 1,wherein, in order to faithfully imitate a multicolored natural rock,multicolored natural sand is deposited on the still moist coat ofsynthetic resin.